Hydraulic press circuit



Jam 28 1941. w. ERNST EYT'AL 2,229,965

HYDRAULIC PRESS CIRCUIT Filed Aug. 16, 1958 2 Sheets-Sheet l I INVENTOFES AT TO I? N KY5 Jan. 28, 1941. w. ERNST ETAL 2,229,965

HYDRAULIC PRESS CIRCUIT Filed Aug. 16, 1958 2 Sheets-Sheet 2 F H l 9' UV VENTORS 7 Wm TEE Exwsr B Y Ida/MA?) 4 1 5:3

[7 /C, 0 HA W 96/ A TTORNE V6 Patented Jan. 28, 1941 UNITED STATES PATENT OFFICE HYDRAULIC PRESS CIRCUIT Application August 16, 1938, Serial No. 225,155

2 Claims.

This invention relates to hydraulic circuits, and in particular, to circuits for regulating the action of hydraulic presses.

' One object of this invention is to provide a 5 hydraulic press circuit having means associated therewith for causing the platen to approach the bed at a relatively rapid speed, and then to slow down when it reaches a predetermined point.

Another object is to provide such a press circuit, wherein the platen operates a valve which cuts oil the free discharge of fluid beneath the double-acting main plunger and forces this fluid to flow through a restricted aperture, thereby slowing up the descent of the press platen when the platen reaches a predetermined position.

Another object is to provide a hydraulic press circuit for controlling the pressing pressure exe'rted by the platen by controlling the pressure at which the shift ring of a variable delivery pump is caused to move to its neutral or zero delivery Position.

Another object is to provide a hydraulic press circuit, wherein the variable delivery pump is provided with a multiple piston servomotor with different areas on the pistons, and means for selectively directing the pressure fluid from the press cylinder to these areas so that the pump flow controlling member or shift ring will be moved to its neutral or zero delivery position at one of a series of selected pressures, depending upon which of the servomotor piston areas is exposed to the action of this pressure fluid.

Another object is to provide a hydraulic press circuit, as described immediately above, wherein the shift from one piston area of the pump servomotor to another piston area thereof is made in response to the action of a timing device so that the press will exert a predetermined pressing pressure for a predetermined length of time, and

40 then will shift to exert another predetermined pressing pressure.

Another object is to provide a hydraulic press circuit having a double-acting main plunger, together with means for utilizing the fluid displaced from one side of this double-acting plunger to operate an auxiliary plunger, without the necessity of employing an additional pump.

Another object is to provide such an auxiliary plunger operating circuit, wherein the auxiliary plunger is caused to move to a predetermined position and then to automatically halt as the fluid supplied thereto reaches a discharge port uncovered by the auxiliary plunger in its motion.

Another object is to provide an auxiliary plunger operating circuit, as described above,

wherein the pump for operating the main plunger performs no work while the main plunger is in its retracted position other than circulating the oil, except when the auxiliary plunger is being moved either in a forward or a reverse direction. 5

In the drawings:

Figure 1 is a diagrammatic view, mainly in section, showing the complete hydraulic press operating circuit of this invention.

Figure 2 is an enlarged diagrammatic view, mainly in section, showing that part of the circult of Figure l for applying different pressures to the press plunger at different periods of time by means of a multiple pressure servomotor pump control system.

General arrangement In general, the hydraulic press operating cir cult of this invention consists of a main circuit having a sub-circuit forming part of the main circuit. The said sub-circuit includes a variable delivery pump with a multiple piston servomotor for moving the pump flow-control member or shift ring to its neutral position when pressure is applied to these different areas, so that the pump is adapted to deliver a plurality of different pressures, depending upon which of the piston areas is exposed to the pressure fluid from the pressing cylinder to shift the pump flow-control member to its neutral position. The action of this multiple servomotor piston, as shown in detail in Figure 2, is opposed by an adjustable spring.

The shifting from one piston area to another is performed by a manual valve, cooperating with 35 a time-responsive valve. The time-responsive valve system consists of a manually operated four-way valve having the supply of air controlled by a solenoidal valve, the solenoid being controlled in turn by a time switch. In this manner the pressure delivered by the pump is of a predetermined degree for a predetermined period of time, after which the valves are shifted so that the servomotor moves the flow-control member to cause the pump to deliver a different predetermined pressure for an additional period of time.

This invention is found to be of great value in certain applications of fluid pressure, where it is desirable to vary the intensity of the applied pressure iln a predetermined manner. In the molding of certain compounds, for example, it has been found desirable to apply a moderate pressure for a time while the molding material softens and partially conforms to the shape of the mold, and thereafter to apply a higher pres sure to force the softened material into the more intricate recesses of the mold so as to fill these recesses fully. The present invention provides means for enabling this to be done, thereby resulting in the production of workpieces of improved quality, particularly where these workpieces are made with molds of intricate shape.

Press construction Referring to the drawings in detail, Figure 1 shows diagrammatically in vertical section a hydraulic press having a bed l0 and head interconnected by side members or uprights |2 at interlocking dove-tail portions l3 and I4, respectively. Mounted upon the press head II is a surge tank l5 for containing and supplying the operating fluid utilized in the circuit. The press head contains a main cylinder borev l6, one end of which serves as a press-advancing chamber l1, and the other end l8 has a press-retracting chamber, these being on opposite sides of the piston head |9 of the main plunger 20. Thus, the main plunger 20 is a double-acting plunger, reciprocating in the cylinder bore l6.

Opening into the press-advancing chamber I1 is a port 2|, providing communication with the interior of the surge tank l5. Mounted in the port 2| is a double-acting surge valve 22, of the type disclosed in the patent to Walter Ernst, No. 1,956,758, of May 1, 1934. The details of this surge valve 22 from no part of the present invention, and its function is as a check valve, which opens when the main plunger 20 starts on its downward stroke under the influence of gravity, so as to permit the rapid traversing of the main plunger 20. The surge valve 22 is provided with a hydraulic motor within the casing portion 23 thereof, this being connected by the conduit 24 with the return chamber 8 beneath the main piston head l9, so as to forcibly open the surge valve 22 and keep it open during the retraction stroke of the main plunger 20. action, as described in the above-mentioned patent, permits the fluid to pass directly from the chamber l1, through the port 2|, back into the surge tank IS without traversing the remainder of the hydraulic circuit. Attached to the main plunger 20 is a platen 25 which moves up and down between the press side members I2 and is guided thereby. The platen 25 is provided with two cam portions 26 and 21 for operating certain valves atpredetermined positions upon the stroke of the platen 25. Surrounding the main plunger 26, for the prevention of leakage therefrom, is a packing 28 compressed by a gland 29.

Multiple pressure pump control sub-circuit The multiple pressure pump-control sub-circuit is shown in the upper right-hand corner of Figure l, and in more detail in Figure 2. This part of the circuit is employed for applying different pressures to the main plunger 20 at different portions of its stroke, for different periods of time. The sub-circuit consists of a variable delivery radial piston pump 30, shown in Figure 1 as mounted upon the side of one of the press uprights 12. Ordinarily, however, this pump 30 is most convenientl mounted upon the head of the press. The pump 30, insofar as its actual pumping mechanism is concerned, is well known to those skilled in the hydraulic art, and is of the type having radial pistons and cylinders with variable strokes, as regulated by the shift ring for shifting the eccentricity of the axis of ro tation of the cylinder barrel with respect to the This secondary rotor for actuating the pistons. Such .a pump is shown in the Ernst Patent No.

2,021,354, of November 19, 1935.

The pump 30 consists of a central casing 3| having therein the pumping mechanism, together with the shift ring for varying the delivery of the pump. This casing 3| is closed by end plates 32, on one of which are mounted the pressure and suction connections 33 and 34, respectively. The pump 38 is driven by any suitable means, such as an electric motor (not shown).

Coaxial with the main pump 30 and driven by the same motor from the shaft thereof, is a slippage pump 35, of any suitable type, such as of the gear type, for providing the low pres- Sure service of pumping slippage fluid from the slippage tank 36, back to the surge tank l5 by means of the conduits 31 and 38, respectively, (Figures 1 and 2). The slippage tank 36 is con nected by the line 39 to the pump casing 3| for the purpose of collecting leakage therefrom, and also by the line 40, to the port 4| immediately above the packing 28 and opposite the perforated drainage ring 42. This ring 42 provides for slippage past the packing 28 from the main cylinder chamber I8.

Mounted upon one side of the main pump casing 3| is a casing 43 having a bore 44 for telescopically receiving a sleeve 45 containing a coil spring 46, abutting the wall 41 at one end of the sleeve 45 and the plate 48 at the other end within the casing 43. Passing through the plate 48 is the pump control rod 49, having a threaded portion 50 thereon engaged by a nut 5|, to which is secured a hand wheel 52, as by the key 53. Arranged between the nut 5| and the end wall 41 of the sleeve 45 is a ball thrust bearing 54. Also mounted upon the threaded portion 50 of the control rod 49 is a lock-nut 55, in the form of a second hand wheel, whereas a nut 56, threaded upon the end of the control rod 49, serves as a retaining nut to retain the parts in position.

The control rod 49 is secured at its inner end to the pump flow-control member or shift ring (not shown), while similarly mounted upon the other end thereof is the servomotor rod 51, carrying thereon the stepped servomotor piston, generally designated 58, reciprocable within the stepped bore, generally designated 59, of the servomotor casing 60 (Figure 2). The servomotor casing 60 is mounted upon the side of the pump casing 3|, in a manner similar to the casing 43. The end of the bore 59 in the casing 60 is closed by an end plate 6| by means of the cap screws 82.

The stepped piston 58 is provided with annular piston areas 63, 64 and 65, formed between the different diameter portions 66 and 61, 61 and 68 and 68 and 69, respectively. The smallest piston area 63 reciprocates within the small diameter bore portion 10, the intermediate piston area 64 within the intermediate bore II, and the large piston area 65 within the large bore portion 12. These bore portions 10, TI and 12 form parts of the stepped bore 59. Adjacent the respective piston areas 63, 64 and 65 their bores 10, H and 12 are widened out in the annular chambers l3, l4 and 15, respectively. Communicating with these chambers are ports I6, I1 and 18, respectively connected to conduits 19, 80 and 8|.

The conduit 19 contains a choke 82 for the purpose of preventing too sudden a shifting of the stepped piston 58 in response to a sudden change of pressure. The stepped piston 58 is held in position by a collar 83, secured upon the rod IiI by the end member 84. The conduit I9 is connected to the conduit 85, leading to the passageway 86 opening into the press-advancing chamber I! of the main cylinder bore IS. The conduits 00 and BI, however, lead to a manually operated fourway valve, generally designated III, at the ports 80 and 09 thereof, respectively. These ports lead into a bore 90 having therein a valverod at with spaced heads 92 and 93. The valve rod 0I emerges through plugs 94, one plug being mounted in the valve casing 95 and the other in the end plate 96 thereof. The valve rod 9i terminates in a handle 91 for the manual manipulation of the valve. The valve bore 90 is provided with annular chambers 98 and 99, adjacent the ports 88 and 89, additional end chambers I00 and IOI being likewise provided and having ports I02 and I03 connected to a discharge conduit I04 leading to the slippage tank 30. The fifth chamber I05 has its port I05 closed by a plug I01.

Pressure fluid is supplied to the conduit 80 by means of a conduit I08, from an air-operated iour-way valve I09 having the valve portions of similar construction and therefore similarly designated as in the four-way valve Bl, with the distinguishing numerals 90 to wi respective- 1y. The valve rod 9| B of the valve I09, however, terminates at one end in an extension IIO surrounded by a coil spring III, engaging a collar II2 secured to the valve rod Ell as at H3. The coil spring III urges the valve rod III downwardly until the collar II2 engages the upper plug 94 The coil spring III at its upper end engages the inner wall of a cap I I4, secured by the screws II5 to the casing 95 of the valve I09. Communicating withthe ports W and I00 is the conduit IIIi, leading downwardly to the slippage tank 36 (Figure 1). On the lower end of the valve rod Ill is mounted a piston head II'I, reciprocable within the bore II8 of an air cylinder II9, mounted upon the lower end of the valve casing 95. This bore H8 is provided with breather ports I20, whereas the opposite end of the air cylinder II 9 is provided with a port IN, to which is connected the conduit I22 leading to the air valve I23, having the valve rod I24 arranged to be shifted by the solenoid I25. The latter is energized by the lines I26 and I2'I, the former leading directly to the electrical supply line I29, whereas the latter leads to the electrical supply line I by way of the time switch I30 and line I3I (Figure 2). The time switch I0 is of any conventional type, and operates a predetermined time after its energization through the lines I3I and I32 to change the energlzation of the solenoid I and to shift the valve rod I24 of the valve I23, opening the con duit I22 to the compressed air conduit I34. With the switch I3I closed, the time switch I starts when the valve I is shifted to commence a pressing stroke, but with the switch I3I open, the time switch I30 starts by the closing of the pressure switch I33 upon the attainment of a predetermined low pressure during the pressing stroke. The variable delivery pump 30 draws in fluid from the surge tank I5 by way of the conduit I35, and discharges pressure fluid through the conduit I31. The globe valve Ilit and the check valve I30 merely serve to prevent the escape of fluid from the surge tank Iii when the pump 30 is disconnected for repairs, or other purposes.

In the operation of the multiple pressure subcircuit shown in Figures 1 and 2, the operator acct It rotates the hand wheel 52 to adjust the compression of the spring 46 to the desired amount suitable for opposing the action of the stepped piston 58, and locks it by turning the loclmut 55. The spring 46 tends to force the flow-control member or shift ring of the pump toward an eccentric position relatively to the pump cylinder barrel, thereby putting the pump on stroke to deliver pressure fluid. When the stepped pis ton 58 is supplied with pressure fluid of a sum-- cient degree to its stepped piston areas 63, 04 or 65, it tends to overcome the force of the spring 46. When a sufficient pressure has thus been built up to overcome the force of the spring, the pump shift ring or flow-control member is moved back to its neutral or no delivery position, compressing the spring 45. Thus, with a given pressure supplied to the stepped piston 59, a lower pressure will be required to overcome the spring force and move the pump to its no delivery position when the pressure is admitted to the larger areas thereof than to a smaller area.

When the pump 30 is started in operation, it delivers pressure fluid through the line I31, to the upper chamber I! of the main cylinder bore I 0, and the main piston head I9 starts down wardly on its pressing stroke in response to the shifting of the main control valve, generally designated I40 (Figure 1). The platen 25 moves downwardly under the influence of gravity upon its weight, and opens the surge valve 22, thereby drawing fluid from the surge tank I5 into the upper chamber I'I. When the platen 25 encounters the workpiece, or other mechanism operated upon, pressure develops within the upper chamber II of the main cylinder bore It, this pressure being transmitted through the passageway 86 and conduits 35 and 19, through the choke 02 to the chamber l3 within the servomotor cating I50, acting against the small diameter annu lar piston area 03. At the same time, pressure fluid also continues onward through the line 85, to and through the valve I09, the valve rod HI and its piston heads 92 and 93 being raised under the influence of air reaching and raising the piston head III within the air cylinder II9. This air comes from the compressed air line I34, through the now open valve I23 and line I22, through the port I 2|, forcing the piston head I II upward. The pressure fluid emerges from the valve I 00. through the conduit I03, and thence through the conduit 00 and port II, into the intermediate chamber I4 of the servomotor casing 00. Here it acts against the intermediate annular piston area 04 upon the stepped piston 00.

at the same time, pressure fluid from the line til passes through the manually operated valve t'I, which the operator has shifted to the right of the position shown in Figure 2 so as to permit this pressure fluid to pass outwardly through the port 00, conduit 8| and port 18, into the upper chamber III of the servomotor casing 00. In this manner the pressure fluid coming from the upper chamber I"! of the main cylinder bore I ii is transmitted simultaneously to all three piston areas 03, I54 and 65 upon the servomotor piston 00. As a large area is exposed to the action of this pressure fluid, a relatively low pressure with in the chamber II will su'llice to overcome the resistance of the coil spring 40, and shift the iiowcontrol member or shift ring of the variable dc livery pump 30 to its neutral or no delivery po sition. The pump, therefore, operates at low pressure so long as the pressure is admitted to Iii all three areas of the servomotor piston 58. If, however, it is desired to operate the press at an intermediate pressure, the hand-operated valve 8'! is shifted to the left, into the position shown in Figure 2. This action closes the valve 81 to the entrance of pressure fluid from the conduit BL, and at the same time opens up the upper chamber I of the servomotor casing 60 to the discharge line I04, by way of the valve chamber 99 in the hand-operated valve 87, thereby rendering ineifective the upper annular piston area 55 upon the servomotor piston 58.

Meanwhile, of course, the time switch I has been energized and is running; At the expiration of the period of time for which the time switch 530 is set, the latter changes the energization of the solenoid I25 so as to shift the valve rod I24 and close the valve I23, thereby cutting on the supply of air to the piston II'I. Accordingly, the valve rod 9 I of the valve I09 moves downwardly, carrying with it its piston heads 02 and 93 into the position shown in Figure 2. This cuts off the valve I09 from the entrance of pressure fluid from the line 85 and opens the middle chamber It to the discharge line H6, so that the fluid from the chamber 14 may flow through the conduits 89, I08 and H6, back to the slippage tank 36. With the upper and middle chambers I5 and M of the servomotor casing 60 thus rendered ineffective, the lower chamber I3 and its annular piston area 63 alone are supplied with pressure fluid. Under these conditions, the pump 30 operates at high pressure since a relatively high pressure is required to be exerted against the annular piston area 63 to overcome the force of the coil spring 36 and to shift the pump flow-control member or shift ring to its neutral or no delivery position. By suitably shifting the handle 97 of the manual valve 81, the operator can selectively apply either a low or an intermediate pressure initially by the pump 30, and follow it up with a high pressure cylinder, a hydraulic plunger in said cylinder, a variable delivery pump connected to said cylinder and having a flow-control member for regulating the delivery of said pump, yielding means for urging said flow-control member in one direction, a servomotor having at least three piston areas adapted to act under pressure in one and the same direction for urging said flow-control memher in a direction opposite to the first mentioned direction, means for establishing constant communication between one of said areas and the press cylinder, a first valve controlling the flow of pressure fluid between the press cylinder and the other two areas simultaneously, a second valve controlling the flow from said first valve to one of said two areas, time-controlled means for operating said first valve, and means responsive to the attainment of a predetermined pressure in said press cylinder for rendering said time-controlled means operative, upon expiration of a pre determined time, for moving said first valve to disconnect said two areas from the press cylinder. 2. In a hydraulic press system, a press having a cylinder, a hydraulic plunger in said cylinder, a variable delivery pump connected to said cylinder and having a flow-control member for regulating the delivery of said pump, yielding means for urging said flow-control member in one direction, a servomotor having at least three piston areas adapted to act under pressure in one and the same direction for urging said flow-control member in a direction opposite to said first-mentioned direction, means for establishing constant communication between the press cylinder and one of said areas, a first valve controlling the flow between the press cylinder and the other two areas simultaneously, a second valve controlling the flow from said first valve toward and from one of said two areas, said second valve being manually operable, time-controlled mechanism for controlling the operation of said first valve, and means responsive to the attainment of a predetermined pressure in said press cylinder for rendering said time-controlled means operative, upon expiration of a predetermined time, for moving said first valve to disconnect said two areas from the press cylinder.

WALTER ERNST.

JOHAN A, MULLER.

VICTOR S. SHAW. 

